Author Topic: BSA C12 Gearbox identification  (Read 876 times)

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Online chaterlea25

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Re: BSA C12 Gearbox identification
« Reply #15 on: February 28, 2019, 08:56:11 pm »
Hi Fred,

a Google search gave me this link, https://www.technobotsonline.com/0.5-inch-steel-chain-sprockets.html
a replacement 16 tooth for £5 approx
I'm sure you can find a "friend" with a lathe and welder  ;D

Are you going to use the bike in trials or on the road? this will decide the size sprocket you need
Also what number of teeth is on the rear wheel ?

The moto cross bike chain I mentioned last night is a 420MBK (for the narrow C10L sprocket)

John

Offline geo

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Re: BSA C12 Gearbox identification
« Reply #16 on: March 02, 2019, 02:14:48 pm »
The standard 19 tooth gearbox sprocket is available from Kidderminster Motorcycles at £17-90 + postage and I've just fitted one to my '56 C12 with no problems.  tel no is 01562 66679, kmc4bsa@hotmail.com  I've always has good & prompt service from that firm. The standard gearing is fine for normal road use in my limited experience.

George Wilson

Offline Fritzele

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Re: BSA C12 Gearbox identification
« Reply #17 on: April 14, 2019, 07:39:49 am »
Hi everyone,

Some good news about the C12's sprocket research :

I found a post on the forum (https://bsac10c11c12.co.uk/smf/technical/gearbox-sprockets/msg32832/#msg32832 ) that give the measurements of the C15 sprocket and it appears that the sprocket for C15 is nearly the same that the one on my C12.

The only difference is the "diamater where seal runs" that is about 40 on the C15 sprocket and 38 on the C12 sprocket.

So, I ordered a C15 sprocket on draganfly, and tried to fit it on the gearbox mainshaft. It was perfect so I juste made it machined at the right size for just just 10 €.

Thanks to eveyone.

Fred


« Last Edit: April 14, 2019, 08:34:41 am by Fritzele »

Online Owen

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Re: BSA C12 Gearbox identification
« Reply #18 on: April 14, 2019, 07:49:28 am »
Please post the C15 sprocket part number so other members can order the same part.
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline Fritzele

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Re: BSA C12 Gearbox identification
« Reply #19 on: April 14, 2019, 09:48:06 am »
Part number is 40-3123. I got it for 26£ on Draganfly. They have it in stock with different amount of teeth.

Online Owen

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Re: BSA C12 Gearbox identification
« Reply #20 on: April 14, 2019, 10:03:13 am »
Cheers,  that makes it easier for people to get. Strange dragonfly haven't sussed that out as its a simple mod like the early to later 3 speed gearbox sprocket needing 1/4" or so shaved off?
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Online chaterlea25

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Re: BSA C12 Gearbox identification
« Reply #21 on: April 14, 2019, 01:27:59 pm »
Hi All,
It would have helped quite a few owners if the linked to post had been followed up on
Back in 2012 ??????
I had totally forgotten that I had posted the C15 dimensions  ::) ::)

It would be a well worthwhile addition to the tech info on the site to add the conversion information

John

Offline Paul S

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Re: BSA C12 Gearbox identification
« Reply #22 on: April 14, 2019, 02:00:30 pm »
Is the step for the oil seal hardened, or could the sprocket be converted on a lathe?
Growing old is compulsory, but growing up is optional.
1955 C12
1961 Greeves Scottish
1998 Kawasaki zzr600
1967 Triumph Vitesse 2 ltr convertible
1959 BSA C1000

Offline Fritzele

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Re: BSA C12 Gearbox identification
« Reply #23 on: April 14, 2019, 03:33:01 pm »
Is the step for the oil seal hardened, or could the sprocket be converted on a lathe?


Sorry, I don't undertstand your question (I'm french). Could you rephrase it ?
« Last Edit: April 14, 2019, 03:38:19 pm by Fritzele »

Online Owen

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Re: BSA C12 Gearbox identification
« Reply #24 on: April 14, 2019, 03:46:54 pm »
Did you turn the diameter down in a lathe or did you have to grind it down?
1940 C12 (350cc)
1945 C10 & C11
1953 C10 & C11
Anyone want a B20 in need of a lot of tlc

Offline timsdad

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Re: BSA C12 Gearbox identification
« Reply #25 on: April 14, 2019, 05:15:27 pm »
When my mate shortened the sprocket  for my Real C12 he just did it in his lathe. No doubt he's got good tooling but it didn't seem to be a problem.

Ray
Just a motorcyclist.

Online camman3

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Re: BSA C12 Gearbox identification
« Reply #26 on: April 14, 2019, 05:34:25 pm »
I turned the face of boss on my 39 c10 sprocket ok with a carbide tipped bit in a little Myford.
It appeared to be case hardened, but a quick plunge through that and it was ok.
Graham
1957 C12
In sunny (sometimes) Christchurch, Dorset, UK

Offline Fritzele

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Re: BSA C12 Gearbox identification
« Reply #27 on: April 14, 2019, 06:53:31 pm »
Did you turn the diameter down in a lathe or did you have to grind it down?

I gave it to a real professionnal machinist who use high tech lathes.

Offline ianinglis

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Re: BSA C12 Gearbox identification
« Reply #28 on: April 14, 2019, 08:46:15 pm »
at the end of the day unless you are going to do 10000 miles a year it will be fine



ian
BSA C10L 1956 - JFO 588
BSA C10L 1954 - MVE 107
RM6 RALEIGH RUNABOUT
ENFIELD DIESEL KUBOTA OC 95
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